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Developing nanocomposites with highly aligned nanoscale reinforcement

Gkaliou, Kyriaki 2021. Developing nanocomposites with highly aligned nanoscale reinforcement. PhD Thesis, Cardiff University.
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In this project the deposition of magnetic nanoparticles onto different graphene morphologies was investigated, to facilitate their alignment in nanocomposites. A simple co-precipitation method was used and detailed chemical analysis confirmed that the synthesis of iron oxide nanoparticles produces a mixed phase of magnetite (Fe3O4)/ maghemite (γ-Fe2O3). Better nanoparticle dispersion and a narrower size distribution was achieved on a higher surface area materials. As the size of the nanoparticles decreases, the ratio of magnetite to maghemite decreases, which leads to a lower magnetic saturation (Ms). The effect of different graphene morphologies on the curing of the epoxy system was investigated by adjusting: (a) the nanofiller loading and mixing methods, (b) the surface functionalisation, (c) the stoichiometric ratio of epoxy resin and (d) the cross-linking density. The nanofillers reduced the density of the epoxy network due to either catalytic interactions with surface functionalization or acting as physical barriers between reacting molecules. This results in a lower stress transfer efficiency in the interphase region and such effects can explain the lower than anticipated reinforcement, especially as filler loading is increased. A comprehensive study developed optimised experimental conditions for magnetic alignment of magnetic graphene flakes. Both theoretical and experimental studies confirmed the orientation of the magnetic flakes in epoxy nanocomposites under low magnetic fields. The alignment effect on the mechanical properties was evaluated using Raman Spectroscopy and tensile measurements. Compared with the nanocomposites containing randomly oriented magnetic flakes, a higher stress transfer between the aligned nanofillers and the matrix was achieved, as well as higher values of stiffness obtained in nanocomposites with certain dispersion state.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Graphene/epoxy nanocomposites; Iron oxide nanoparticles; Curing effects; Magnetic alignment ;Mechanical properties; Dynamic Mechanical Analysis
Date of First Compliant Deposit: 28 July 2021
Last Modified: 02 Aug 2022 01:15

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